Thread feeding device of a sewing machine

ABSTRACT

A thread feeding device of a sewing machine includes a needle bar movable vertically to pull an upper thread through a fabric, and movable between left and right terminal positions. An imaginary plane to which the needle bar is normal is defined, and includes left and right boundary lines which pass through the left and right terminal positions. An inner rotary hook includes a thread tensing unit disposed on a hook surrounding wall. A lower thread passes through and abuts against the thread tensing unit to define at least one thread abutting point. A final abutting point where the lower thread passes through the thread tensing unit immediately before reaching the fabric is defined, and is projected on the imaginary plane at a point that is interposed between the boundary lines.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No. 109128979, filed on Aug. 25, 2020.

FIELD

The disclosure relates to a household sewing machine, and more particularly to a thread feeding device of a sewing machine.

BACKGROUND

A bobbin thread feeding device of a household sewing machine as disclosed in US 2010/0126398 includes a needle bar driven to move vertically to pull an upper thread through a fabric, an outer rotary hook horizontally rotating in synchronization with the vertical movement of the needle bar, an inner rotary hook contained in the outer rotary hook and not to rotate in synchronization with the outer rotary hook, and a lower thread bobbin contained in the inner rotary hook. The outer rotary hook catches the upper thread that extends through the needle bar and brings the upper thread into intertwining with a lower thread pulled out of the bobbin for sewing on the fabric. Thus, the fabric is placed below the needle bar and is pushed along a sewing direction for sewing. Moreover, in a conventional sewing machine, the needle position of the needle bar is adjustable in a left-and-right direction that is perpendicular to the sewing direction so as to form various patterns by moving the fabric along the sewing direction.

However, due to the inner rotary hook in the form of a horizontal rotary hook, the intertwining of the threads is uneven and not uniform. As shown in FIG. 1, the upper thread 91 and the lower thread 92 are sewed on the fabric 93 along a sewing direction (X). The upper thread 91 is intertwined with the lower thread 92 to form loops 911. As demonstrated in FIG. 1, the loops 911 on a left side are larger in dimension than those on a right side.

SUMMARY

Therefore, an object of the disclosure is to provide a thread feeding device that can alleviate at least one of the drawbacks of the prior art.

According to the disclosure, the thread feeding device of a sewing machine is adapted for feeding upper and lower threads to a fabric. The lower thread is supplied from a lower thread bobbin. The thread feeding device includes a needle bar and an inner rotary hook. The needle bar is driven to move in an up-and-down direction between an upper position and a lower position to pull the upper thread through the fabric. The needle bar is movable in a left-and-right direction which is perpendicular to the up-and-down direction between a left terminal position and a right terminal position. The needle bar defines an imaginary plane to which the needle bar is normal and which extends in a front-and-rear direction that is perpendicular to both the up-and-down direction and the left-and-right direction. The imaginary plane includes a left boundary line which extends in the front-and-rear direction and passes through the left terminal position, and a right boundary line which extends in the front-and-rear direction and passes through the right terminal position. The inner rotary hook is disposed below the fabric. The inner rotary hook includes a hook base wall, a hook surrounding wall which surrounds the hook base wall to cooperatively define an accommodation chamber with an upwardly facing opening, and a thread tensing unit which is disposed on the hook surrounding wall. The lower thread bobbin is disposed in the accommodation chamber to supply the lower thread such that the lower thread is pulled out from the lower thread bobbin and passes through the thread tensing unit to reach the fabric. The thread tensing unit is provided with at least one thread abutting point where the lower thread abuts against and is tensed. The at least one thread abutting point includes a final abutting point where the lower thread passes through the thread tensing unit immediately before the lower thread reaches the fabric. The final abutting point is projected on the imaginary plane in the up-and-down direction at a projected point. The projected point is interposed between the left boundary line and the right boundary line.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings, of which:

FIG. 1 is a schematic view illustrating a sewing stitch of a conventional sewing machine;

FIG. 2 is a fragmentary perspective view illustrating a first embodiment of a thread feeding device of a sewing machine according to the disclosure and upper and lower threads;

FIG. 3 is an exploded perspective view of the first embodiment;

FIG. 4 is a schematic top view of the first embodiment;

FIG. 5 is a sectional view taken along line V-V of FIG. 4;

FIG. 6 is a front view of a thread tensing plate of the first embodiment;

FIG. 7 is a schematic view illustrating a sewing stitch of the first embodiment;

FIG. 8 is a schematic top view illustrating a second embodiment of the thread feeding device according to the disclosure;

FIG. 9 is a front view of a thread tensing plate of the second embodiment; and

FIG. 10 is a schematic top view illustrating a third embodiment of the thread feeding device according to the disclosure.

DETAILED DESCRIPTION

Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.

Referring to FIGS. 2 to 4, a first embodiment of a thread feeding device of a sewing machine according to the disclosure is adapted for feeding upper and lower threads 81, 82 to a fabric 83. The lower thread 82 is supplied from a lower thread bobbin 84. The thread feeding device includes a needle bar 1 and an inner rotary hook 2.

The needle bar 1 is driven to move in an up-and-down direction (D1) between an upper position (as indicated in a solid line of FIG. 2) and a lower position (as indicated in a dash-dotted line of FIG. 2) to pull the upper thread 81 through the fabric 83. The needle bar 1 is further movable in a left-and-right direction (D2) which is perpendicular to the up-and-down direction (D1) between a left terminal position (as indicated in a solid line of FIG. 4) and a right terminal position (as indicated in a dash-dotted line of FIG. 4). The needle bar 1 defines an imaginary plane (A) to which the needle bar 1 is normal and which extends in a front-and-rear direction (D3) that is perpendicular to both the up-and-down direction (D1) and the left-and-right direction (D2). The imaginary plane (A) includes a left boundary line (BL) which extends in the front-and-rear direction (D3) and passes through the left terminal position, and a right boundary line (BR) which extends in the front-and-rear direction (D3) and passes through the right terminal position. In this embodiment, the left and right boundary positions indicate the positions where the extreme movement of the needle bar 1 can be achieved in the left-and-right direction (D2).

With reference to FIGS. 2, 4 and 5, the inner rotary hook 2 is disposed below the fabric 83, and includes a hook base wall 21, a hook surrounding wall 22 which surrounds the hook base wall 21 to cooperatively define an accommodation chamber (P) with an upwardly facing opening, and a thread tensing unit 23 which is disposed on the hook surrounding wall 22. The lower thread bobbin 84 is disposed in the accommodation chamber (P) to supply the lower thread 82 such that the lower thread 82 is pulled out from the lower thread bobbin 84 and passes through the thread tensing unit 23 to reach the fabric 83.

The thread tensing unit 23 includes a thread tensing plate 24 which is disposed on an inner circumferential surface of the hook surrounding wall 22, and a thread tensing spring 25 which is interposed between the inner circumferential surface of the hook surrounding wall 22 and the thread tensing plate 24. The thread tensing plate is arc in shape and extends along the inner circumferential surface of the hook surrounding wall 22 to have a fixed portion 241 and a thread pull-out portion 242 opposite to each other along the inner hook surrounding wall 22. The fixed portion 241 is fixed on the hook surrounding wall 22. The thread pull-out portion 242 is spaced apart from the inner circumferential surface of the hook surrounding wall 22. A thread hole 243 is formed in and penetrates the thread pull-out portion 242. A thread cutout 244 is formed in an upper edge of the thread pull-out portion 242 and is not in communication with the thread hole 243. A guiding slit 245 (see FIG. 6) is a cutout from an upper edge of the fixed portion 241 and extends downwardly and to the thread pull-out portion 242 to communicate with the thread hole 243. In this embodiment, the thread tensing plate 24 is mounted such that, in a view from a top of the inner rotary hook 2, the thread pull-out portion 242 is a leading side of the fixed portion 241 in a counterclockwise direction. The thread tensing spring 25 is also arc in shape, and has a fixed end 251 which is fixed on the fixed portion 241 of the thread tensing plate 24, and a suspending end 252 which is spaced apart from both the inner circumferential surface of the hook surrounding wall 22 and the thread pull-out portion 242.

The lower thread 82 that is pulled out of the lower thread bobbin 84 is guided by the guiding slit 245 and then passes through the thread hole 243. A segment of the lower thread 82 that extends from the thread hole 243 abuts against the thread pull-out portion 242 and is tensed in the thread cutout 244. The segment of the lower thread 82 is gripped by the suspending end 252 and the thread pull-out portion 242 so as to impart an appropriate tension to the lower thread 82.

Specifically, the thread tensing unit 23 is provided with at least one thread abutting point (E) where the lower thread 82 abuts against and is tensed. In this embodiment, the lower thread 82 abuts against the thread tensing unit 23 at only one position such that a final abutting point (F) where the lower thread 82 passes through the thread tensing unit 23 immediately before the lower thread 82 reaches the fabric 83 is defined as the same thread abutting point (E). That is, only one thread abutting point (E) is provided in this embodiment. Moreover, the final abutting point (F) is projected on the imaginary plane (A) in the up-and-down direction (D1) at a projected point. The projected point is interposed between the left boundary line (BL) and the right boundary line (BR). Furthermore, in this embodiment, a distance from the projected point of the final abutting point (F) to the left boundary line (BL) is substantially the same as a distance from the projected point of the final abutting point (F) to the right boundary line (BR).

In various other embodiments, the thread tensing unit 23 may be provided with a plurality of thread abutting points (E) which are set in accordance with the passing course of the lower thread 82, and one thread abutting point (E) where the lower thread 82 passes through the thread tensing unit 23 immediately before the lower thread 82 reaches the fabric 83 is defined as the final abutting point (F). It should be noted that only the projected point of the final abutting point (F) should be interposed between the left boundary line (BL) and the right boundary line (BR).

The upper thread 81 is intertwined with the lower thread 82 to form loops with the lower thread 82, and the lower thread 82 is then bound next to the needle bar 1. At this phase, the intertwined angle of the upper and lower threads 81, 82 is determined by the relational positions of the final abutting point (F) and the needle bar 1. Taking FIG. 4 as an example, in the first embodiment, a first intertwined angle (S1) is defined when the needle bar 1 is located at the left terminal position, and a second intertwined angle (S2) is defined when the needle bar 1 is located at the right terminal position. Since the distance from the final abutting point (F) to the left boundary line (BL) is substantially the same as the distance from the final abutting point (F) to the right boundary line (BR), the first intertwined angle (S1) is the same as the second intertwined angle (S2). Thus, the loops 811 generated from the upper thread 81 are formed evenly and with an equal dimension so as to render the intertwining of the threads even and uniform, as shown in FIG. 7. Specifically, the loops 811 generated from the upper thread 81 during intertwining with the lower thread 82 are formed uniformly and evenly.

It should be noted that the distance from the final abutting point (F) to the left boundary line (BL) is preferably the same as the distance from the final abutting point (F) to the right boundary line (BR), but these distances should not be limited thereto.

Referring to FIGS. 8 and 9, in a second embodiment, the thread tensing plate 24 which has a different configuration is mounted such that, in a view from a top of the inner rotary hook 2, the thread pull-out portion 242 is a leading side of the fixed portion 241 in a clockwise direction.

Referring to FIG. 10, in a third embodiment, the thread tensing unit 23 further includes an abutting member 26 which is disposed on the hook surrounding wall 22. The abutting member 26 has a thread abutting portion 261 which is located at a route of the lower thread 82 and interposed between the thread tensing plate 24 and the fabric 83.

In this embodiment, once the needle bar 1 is located at the left terminal position, the lower thread 82 that is pulled out from the lower thread bobbin 84 passes through one thread abutting point (E) in the thread cutout 244 and then passes through another thread abutting point (E) on the thread abutting portion 261. Since the lower thread 82 passes through the thread abutting portion 261 immediately before the lower thread 82 reaches the fabric 83, the thread abutting point (E) at the thread abutting portion 261 is defined as the final abutting point (F) and is located between the left boundary line (BL) and the right boundary line (BR).

As illustrated, with the projected point of the final abutting point (F) on the imaginary plane (A) in the up-and-down direction (D1) being interposed between the left boundary line (BL) and the right boundary line (BR), the upper thread 81 can be intertwined with the lower thread 82 to form the loops evenly and uniformly.

While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

What is claimed is:
 1. A thread feeding device of a sewing machine for feeding upper and lower threads to a fabric, the lower thread being supplied from a lower thread bobbin, said thread feeding device comprising: a needle bar driven to move in an up-and-down direction between an upper position and a lower position to pull the upper thread through the fabric, said needle bar being movable in a left-and-right direction which is perpendicular to the up-and-down direction between a left terminal position and a right terminal position, said needle bar defining an imaginary plane to which said needle bar is normal and which extends in a front-and-rear direction that is perpendicular to both the up-and-down direction and the left-and-right direction, the imaginary plane including a left boundary line which extends in the front-and-rear direction and passes through the left terminal position, and a right boundary line which extends in the front-and-rear direction and passes through the right terminal position; and an inner rotary hook disposed below the fabric, said inner rotary hook including a hook base wall, a hook surrounding wall which surrounds said hook base wall to cooperatively define an accommodation chamber with an upwardly facing opening, and a thread tensing unit which is disposed on said hook surrounding wall; the lower thread bobbin being disposed in said accommodation chamber to supply the lower thread such that the lower thread is pulled out from the lower thread bobbin and passes through said thread tensing unit to reach the fabric, said thread tensing unit being provided with at least one thread abutting point where the lower thread abuts against and is tensed, said at least one thread abutting point including a final abutting point where the lower thread passes through said thread tensing unit immediately before the lower thread reaches the fabric, said final abutting point being projected on the imaginary plane in the up-and-down direction at a projected point, the projected point being interposed between the left boundary line and the right boundary line.
 2. The thread feeding device as claimed in claim 1, wherein a distance from the projected point of said final abutting point to the left boundary line is substantially the same as a distance from the projected point of said final abutting point to the right boundary line.
 3. The thread feeding device as claimed in claim 1, wherein said thread tensing unit includes a thread tensing plate which is disposed on an inner circumferential surface of said hook surrounding wall, said thread tensing plate including a fixed portion which is fixed on said hook surrounding wall, a thread pull-out portion which extends from said fixed portion and which is spaced apart from said inner circumferential surface of said hook surrounding wall, a thread hole which is formed in and penetrates said thread pull-out portion, and a thread cutout which is formed in an upper edge of said thread pull-out portion and which is not in communication with said thread hole for the lower thread that is pulled out of the lower thread bobbin to pass through said thread hole and abut against said thread pull-out portion in said thread cutout.
 4. The thread feeding device as claimed in claim 3, wherein said thread tensing unit further includes a thread tensing spring which is interposed between said inner circumferential surface of said hook surrounding wall and said thread tensing plate, said thread tensing spring having a fixed end which is fixed on said fixed portion of said thread tensing plate, and a suspending end which is spaced apart from both said inner circumferential surface of said hook surrounding wall and said thread pull-out portion such that a segment of the lower thread that extends from said thread hole to said thread cutout is gripped by said suspending end and said thread pull-out portion so as to impart a tension to the lower thread.
 5. The thread feeding device as claimed in claim 3, wherein said thread tensing plate further includes a guiding slit which is a cutout from an upper edge of said fixed portion and extends downwardly and to said thread pull-out portion to communicate with said thread hole.
 6. The thread feeding device as claimed in claim 3, wherein said thread tensing plate is arc in shape and extends along said inner circumferential surface of said hook surrounding wall to have said fixed portion and said thread pull-out portion, said thread tensing plate being mounted such that said thread pull-out portion is a leading side of said fixed portion in a counterclockwise direction in a view from a top of said inner rotary hook.
 7. The thread feeding device as claimed in claim 3, wherein said thread tensing plate is arc in shape and extends along said inner circumferential surface of said hook surrounding wall to have said fixed portion and said thread pull-out portion, said thread tensing plate being mounted such that said thread pull-out portion is a leading side of said fixed portion in a clockwise direction in a view from a top of said inner rotary hook.
 8. The thread feeding device as claimed in claim 3, wherein said thread tensing unit further includes an abutting member which is disposed on said hook surrounding wall, said abutting member having a thread abutting portion which is located at a route of the lower thread and interposed between said thread tensing plate and the fabric such that a segment of the lower thread that passes through said thread cutout abuts against said thread abutting portion to define said final abutting point at said thread abutting portion. 